The propsed research is designed as an analytical and manipulative investigation of mechanisms critical to cell migration in the patterning of the developing nervous system. The studies will focus on two developing cranial nerve nuclei in the chick embryo. the oculomotor ventromedial subnucleus and the trigeminal motor nucleus. In studying the patterns of migration and possible mechanisms important for the proper execution of these patterns, a combination of approaches will be used, including interspecific embryonic transplantation, sequential electron microscopic analysis of intercellular interactions dueing disparate migration phases, analysis of cellular-substrate interactions, and dual embryonic microsurgical-autoradiographic study. Within the oculomotor ventromedial subnucleus, the experiments will determine the pattern of migration whereby the primordial cells attain their definitive position, the nature and sequence of intercellular contacts formed during migration, (both within and between populations), and will examine pinocytosis as a possible mechanism for mediation of guided cell movement. within the trigeminal moto nucleus, the proposed studies will examine the nature and sequence of intercellular contacts formed prior to, during and after migratton and will experimentally analyze the importance of extracellular influences (i.e., ingrowing ganglionic afferents) to migration of this nucleus. Much of this research derives from preliminary study by the applicants which has suggested points at which critical events may be taking place and which has begun to reveal certain categories of mechanisms which may prove to be important to themigration proces. It is felt that these studies, particularly in their use of a multi-varied approach, will contribute significantly to an understanding of the migration phenomenon as a process basic to normal nervous system development.